Heretofore in the use of caster rolls in steel mills and the like from time to time the rolls become damaged by scars, scratches or cracks and must be reconditioned. Heretofore rolls of this nature are machined by an undercut into the roll surface sufficient for ultrasonic or magnetic particle inspection purposes. Often times an inspection will indicate that the roll is reusable merely by machining to a finished diameter. In other situations the roll will have cracks or gouges therein which will require welding prior to final machining. An initial step in such process is to stress relieve the roll by placing it in a furnace and gradually bringing its temperature up to 750.degree. to 800.degree. F. and soaking it for 2 to 3 hours and gradually cooling to ambient temperature. This is followed by an ultrasonic inspection of the roll for crack determination and location. This is followed by the step of machine gouging the cracks along the length of the roll and throughout its circumference and thereafter machine undercutting the surface in order to receive a weld build up and weld overlay. This has been conventionally followed by a preheat of the roll wherein the roll has been gradually and uniformly heated at approximately 150.degree. F. per hour to the required welding preheat temperature of about 600.degree. F. minimum.
After the roll has been preheated, it is transferred to a roll welding machine which includes a power rotated head stock and tail stock for supporting the roll upon its longitudinal axis and heat is applied to the roll in order to maintain its preheat temperature and interpass temperatures of 600.degree. F. approximately during all welding operations.
Heretofore there has been the problem of continually maintaining the roll at this minimum preheat temperature with the result that failure to maintain such preheat temperature can produce stress, inequalities or imperfections in the roll surface at the welds over portions thereof, particularly at cracks and produce stresses of non-uniform character, so that the roll is suscepticle to early damage in subsequent use. The problem has existed therefore of providing a continuous preheat temperature in the range of 600.degree. F. and for providing assurance continuously that the roll during its welding has maintained this continuous temperature and therefor providing a visual indication of such and also providing a record of the heat treatment and welding of the roll for future inspection as to verification as to whether the welding steps were applied to the steel roll and possibly explain why a roll broke down too soon for lack of maintenance of the preheat temperature during all welding procedures.